A bright star made right-angle turns without deceleration and sped down over the horizon.

My wife and I were viewing the stars outside a friend's home on a hilltop in rural Maine.  I was watching a medium sized bright yellowish star moving slowly in a straight line from East to West directly overhead and was trying to determine if it was a plane.  It appeared to be as far away as the stars. 
I asked ((female name deleted)) to look and we both watched as the star, just a steady bright light with no blinking, made a perfect right-angle turn towards the North with no deceleration whatsoever, travelled for around 10 seconds in a straight line Northward, and then made another right-angle turn Westward, travelled in a straight line Westward for 5 seconds and then accelerated and zoomed towards and over the horizon. 
At no time did we see sparks or any sort of trail like a meteor would make.  It was just a yellowish star doing something I couldn't since find any way of explaining.